Field of the Invention
The present invention relates to a transmission.
Discussion of the Background
A dual clutch type transmission (twin clutch type transmission) includes, as a basic configuration, a first input shaft on which a plurality of driving gears (hereinafter, referred also to as speed change gear or gears) of an odd number shift stage are arranged in a relatively rotatable manner, a second input shaft on which a plurality of driving gears of an even number shift stage are arranged in a relatively rotatable manner, a first synchromesh mechanism or a second synchromesh mechanism for allowing each of the driving gears to be synchronously engaged with the first input shaft or the second input shaft to which each of the driving gears belongs, an output shaft on which a plurality of driven gears configured to be engaged with the driving gears of the odd number shift stage and the diving gears of the even number shift stage are arranged, and a first clutch or a second clutch for connecting and disconnecting drive force between a drive source and the first input shaft or the second input shaft.
A speed change process of the dual clutch type transmission is composed of a shift preparation (pre-shift), a changeover of a clutch (changeover of clutch connection) and a shift release. The shift preparation is a state of allowing the speed change gear of a next shift stage (hereinafter, referred also to a target shift stage) to be previously engaged with the input shaft (hereinafter, referred also to as another shaft) which does not contribute to current traveling, during a period in which the speed change gear of a current shift stage is synchronously engaged with the input shaft (hereinafter, referred also to a current traveling shaft) which contributes to the current traveling. Further, the changeover of the clutch is a state of releasing the clutch of the current traveling shaft (hereinafter, referred also to a current stage clutch) and fastening the clutch of another shaft (hereinafter, referred also to a next stage clutch) thereby to have the target shift stage fixed as the current shift stage. Moreover, the shift release is a state of returning the synchromesh mechanism of a previous shift stage (hereinafter, referred also to a former shift stage) to a neutral position thereby to release the synchronous engagement of the speed change gear of the former shift stage with another shaft.
By the way, there is known the dual clutch type transmission which has a motor combined with a shaft end of the first input shaft on the downstream side of the first clutch in order to assist drive force of an engine by torque of the motor or to allow a vehicle to travel only by the torque of the motor (see Japanese Patent Application Laid-Open Publication No. 2011-20575, for example)
In the dual clutch type transmission provided with the motor, when the first synchromesh mechanism is in the neutral state and the second synchromesh mechanism in an in-gear state, the second clutch is fastened and the drive force of the engine is transmitted to drive wheels through the second input shaft so as to move the vehicle forward.
Further, during the traveling of the vehicle, the first clutch is fastened and electric power is generated through the first input shaft by the drive force of the engine whereby to allow a battery to be charged with the electric power. To put it briefly, the vehicle can travel in a state of fastening each of the first clutch and the second clutch at the same time.
Accordingly, for example, during traveling at the even number shift stage by fastening the second clutch, in the case where remaining capacity of the battery is small, it is possible to fasten the first clutch and drive the motor as a generator by the drive force of the engine thereby to charge the battery. Further, when the vehicle is stopped in the neutral states of the first and second synchromesh mechanisms, it is possible to shift a second speed gear to the second input shaft and fasten the second clutch during charging the battery by fastening the first clutch, so as to start the vehicle at the second shift stage.
Like this, in the above dual clutch type transmission, the fastening and release of the clutches are performed frequently during the traveling and stopping of the vehicle. FIG. 7B is a graph showing time series datum at the time of rotation of the engine and the second clutch and each of time series datum of rotation amplitude of the second clutch, torque amplitude of a drive shaft and vibration amplitude of the vehicle body in the case where the second clutch has been fastened and the vehicle has been started at the second shift stage during the stopping of the vehicle when each of the first and second synchromesh mechanisms is in the neutral position. Herein, the time series datum of the rotation of each of the engine and the second clutch are indicated by time series datum of rotational frequency, and each of the time series datum of the rotation amplitude of the second clutch, the torque amplitude of the drive shaft and the vibration amplitude of the vehicle body is indicated by a time series data of fluctuation in which each of time series datum of rotational frequency, torque and vibration is extracted by a band pass filter.
It is apparent from the drawing that, when the second clutch starts to be fastened at the time t1, the drive force (rotation) from the engine fluctuates and becomes the rotational fluctuation of the second clutch thereby to be transmitted to the drive shaft. In other words, it is clear that the rotational fluctuation of the drive force attendant on the clutch fastening is easily subject to being directly transmitted to the drive shaft.
By the way, there is proposed a method for suppressing the rotational fluctuation of the drive force attendant on the clutch fastening, by the torque of the motor (for example, see [0082] to [0084] of Japanese Patent Application Laid-Open Publication No. 2011-20575).